Telecommunications, spectroscopy, laser printing, biological tissue analysis, and metrology are just some of the applications that benefit from high-power, single-mode on-chip lasers with good beam qualities. Distributed feedback (DFB) lasers and vertical-cavity surface-emitting lasers (VCSELs) rely on one-dimensional feedback structures to provide relatively high-power, single-mode beams. Unfortunately, these lasers suffer from intrinsic drawbacks: DFB lasers and other edge-emitting sources tend to suffer from catastrophic optical damage at their facets, and the VCSELs' output powers are usually limited by their small cavity sizes.
Two-dimensional distributed feedback enables broad-area, single-mode operation from surface emitters, including photonic-crystal surface-emitting lasers (PCSELs). PCSELs are essentially two-dimensional versions of second-order DFB lasers, where the higher quality factor lasing mode is selected through symmetry mismatch to the free-space modes. In particular, PCSELs have achieved high surface-emitting single-mode power and the ability to control the shapes, polarizations, and directions of their far-fields. However, the lasing areas of PCSELs are limited by two fundamental constraints. First, the mode spacing decreases as the cavity area increases, which promotes multi-mode lasing. Second, the distributed in-plane feedback localizes the lasing fields to individual sections, which promotes multi-area lasing. Since the output power scales with the lasing area, these constraints limit the maximum output power of a single-mode beam emitted by a PCSEL.